Bond length optimum

One after the other, examine methanol dimer and acetic acid dimer. Do the hydrogen-bond lengths in these systems differ significantly from the optimum distance in water dimer Are the hydrogen-bond angles in these compounds significantly different from those in water dimer Rationalize your results. 

How close are the two nuclei in the H2 molecule If they are too close, they will repel each other because both are positively charged, yet if they re too far apart, they won t be able to share the bonding electrons. Thus, there is an optimum distance between nuclei that leads to maximum stability (Figure 1.9). Called the bond length, this distance is 74 pm in the H2 molecule. Every covalent bond has both a characteristic bond strength and bond length. 

Independent of the conformation, the bond multiplicity must be only two. If the shorter distances are a requirement for optimum overlap for ti-MOs, these requirements must also exist in multiple bonds involving a- and 7t-bonds. The 7t-bonds, however, are forced by the overwhelming a-bonds to be at non-optimal overlapping distances. While there are many factors that contribute to the observed bond lengths in a binuclear transition metal complex, shorter distances would be mandated by n- and 8-MOs for optimum overlap. The 7t-alone-bonding proposed for Fe2(CO)6 allows 71-bonds to attain their natural shorter distances. The overlap of... 

There is always an optimum distance for the two bonded nuclei. If they are too far apart, their attraction for the bonding electrons is diminished. If they are too close together, their electrostatic repulsion pushes them apart. The intemuclear distance where attraction and repulsion are balanced, which also gives the minimum energy (the strongest bond), is the bond length. 

There are lateral motions up to — 2 A, and some buckling in the third layer to maintain optimum bond-lengths and angles. 

Bond length is the optimum distance between nuclei. 

---